Insulated electrical conductor



May 11, 1937. G. s. OBDELL 2,079,943

I `INSULATED ELECTRICAL CONDUCTOR Original Filed Oct. 26, 1932 ATTORNEY`Patented May 11, 1937 l 2,079,943

INSULATED ELECTRICAL CONDUCTOR George Spencer Lobdell, Rome, N. Y.,assig'nor to General Cable Corporation, New York, N. Y., a V corporationof New Jersey Application October 26, 1932, Serial No. 639,594

Renewed June 1, 1936 16 Claims. (Cl. 173-264) This invention relates toinsulated electrical In chemical plants, rubber-insulated wires andconductors. It is an object of the invention to cables must be replacedat short intervals beprovide improved insulated conductors. Other causeof the injurious effects of acids and alkalis objects and advantages ofthe invention will on the rubber. The problem in chemical plants appearhereinafter. is of such moment that wherever possible bare 5` Anillustrativeembodiment of the invention conductors are being substitutedfor insulated selected merely for descriptive purposes is shownconductors because of the short life of rubber in th'e accompanyingdrawing, in which: and other known insulating materials.

Fig. 1 is an enlarged longitudinal elevation of This plastic substancehas a further important 10 4a section of insulated conductor with theinsu-V advantageover rubber as an electrical insulating 10 lating layersremoved progressively greater dismaterial for the reason that thisplastic subtances to disclose the construction; D stance is very highlyresistant to injuryvby the Fig.-2 is a section through the conductor oeffects of electrical corona. In rubber-insulated Fig. 1 substantiallyon the line 2 2; conductors used at medium or high voltages, par- Fig. 3is an enlarged longitudinal elevation of ticularly if the rubber is alsounder physical stress l5 Vanother se'ction of insulated conductor withthe s uch as is caused by bending the conductors, the insulating layersremoved progressively greater o'zone which is formed by the corona cutsand distances to disclose the construction; and destroys the rubber.Experimental tests have Fig. 4 is a section through the conductor ofshown that this plastic substance is substantially f Fig. 3substantially on the line 4 4. unaffected by corona, and that for thesame 20 This application is a continuation in part of thickness ofinsulation it may be used at high my application Serial No. 619,410,filed June 27, voltages and under physical conditions which 1932. areprohibitive for rubber.

The plastic substance disclosed in Canadian When used for insulatingelectrical conduc- Letters Patent No. 290,645, June 18, 1929, to Jotors,these olen polysulfide reaction products 25 a seph C. Patrick, consistsmainly of organically desirably are mixed with fillers and curing agentscombined sulfur. This plastic substance may be in somewhat the samemanner as rubber. 'I'he formed by the interaction of halogen additivecomterm "olefin polysulfide reaction products is used pounds of olefinswith polysuliides, for example. herein to include such mixtures in thesame sense by the interaction of ethylene dichloride and sothat .irubberis used as a broad term to include 30 dium polysulde, and merelyk forconvenience in mixtures of pure rubber with fillers and curingdescription may be described as an olen polysulagents. dereactionproduct, and inthe exemplary case g Olefin polysulfide reaction productsmay be as a condensation product of ethylene dichloride cured by heatingin a manner somewhat similar and an alkali pOlySlllde- ThiSySllbStanCe,WhiCh to that used in curing rubber, as by the open -is a'combinationofcarbon, hydrogen and sulfur, steam process, but when so cured theresultant has ,certain physical properties resembling those substance isvery SpOngy and porous. Although of rubber. 'I'he hardness of thissubstance may olefin polysulflde reaction products are cured by VaryOVel a Wide fange, dependent 0n the Sulfur heating, the word cured hasan entirely differ- 40 COD'Ilt, flOm a hard DlOdllCi? t0 a Soft elasticent significance than when used with reference 40 those of rubber in anumber of important reoften is desirable that the insulation ofelectrical product. For the insulation of flexible electrical to rubber,1u the case of fumery buying comconductors the sulfur content desirablyis about prises the combination of the rubber with sulfur .82% t0 33%-whereas inthe case of olefin polysulde reaction The Properties 0f thlssubstance infer from products, curing comprises the production ofastable chemical compound from an unstable form 45` of the same compound.Cured olefin polysulde reaction products loaded suciently to.'reduceporosity have a low resistance to fatigue and crack rather easily, andthe dielectric qualities 50 conductor@ be immune to attack by oils,acids, are not satisfactory for use in insulatingelectrical alkalis andorganic solvents. For example, rub- Conductors. During the Curlng 0fOlen polyslllber-insulated ignition wire used in internal comfidereaction products by theheat process a .disbustion engines deterioratesrapidly because of agreeable gaseous decomposition product .is givenspects. This plastic substance is highly resistant to decomposition byoils, acids and alkalis, and is substantially insoluble in practicallyall known acids, alkalis and organic solvents. It

the oil which comes in contact with the rubber. off having thecharacteristics of tear gas. The 55 formation of this gas makes thehandling and curing of the substance more diiilcult.

The diiculties encountered in curing olen polysuliide reaction productsmay bepartially overcome by the addition of rubber. It has been foundthat the addition of very small quantities of rubber does not seriouslyaffect the resistance of the resulting mixture to oils, acids, alkalis,and organic solvents. However, if rubber is added in sufficientquantities to materially reduce the porosity and sponginess of the curedproduct, the resistance to oil and to the effects of electrical coronaare greatly reduced.

It is believed that the objectionable porosity and sponginess in thecured olen polysulde reaction products is caused by the formation of thegaseous decomposition product, probably a thio-aldehyde, in thesubstance during the heating process. Other substances may be added toaccelerate the curing of the oleiin polysulde reaction products, but inthe manufacture of insulated wires it is impractical to use anaccelerator sufficiently rapid to eect complete curing of the substancebefore gas is formed in any substantial quantity. The reason for this isthat.

the use of such a rapid accelerator would result in the precuring of thesubstance on the rolls and in the extruding machines before thesubstance is on the wire. Furthermore, such a rapid accelerator wouldresult in any rubber in the mixture being overcured.

Applicant has found that olefin polysulfide reaction products may beheat treated to give a substantially non-porous product by adding to thecompound before heating another substance which substantially preventsthe formation of free gas in the compound. It is believed that this-added substance combines with the gaseous decomposition product to forma condensation product with a low vapor pressure, thereby substantiallypreventing the formation of pores and holes in the compounds. Suchsubstances are found in the classes of primary aromatic amines,naphthylamines, naphthols and phenols, and contain the group NH2 or thegroup OH combined with radicals which so limit the activity of thesegroups as to cause the prevention of gas formation to take place under.curing conditions. In this use the chemical activity of the individualmembers of these classes varies, and therefore the most effective memberof these series of compounds is determined by the conditions of curingthe oleiin polysulfide reaction products. For

example, applicant has found that a small amount of orthotoluidineincorporated inl` an olen polysulde reaction product before" curingpermits curing in a solid, non-porous compound in open steam. Onesuitable mixture for a cure of fty minutes at 287 F. is as follows:

This compound has excellent electrical properties and exhibits a highresistance to oils, acids, alkalis and organic solvents. b

If the electrical properties are not of primary importance, as where thecompound is to be used as a sheath enclosing an insulated conductor, adifferent mixture may be preferable. In such a compound it is desirablethat the resistance to oils, acids, alkalis land organic solvents be amaximum. One suitable mixture for a cure of 50 minutes at 287 F. is asfollows: Olen polysulde reaction product gm 500 Smoked 'sheets gm..- 50Diphenyl-guanidine gm 4.5 Orthotoluidine c'.c 5 Zinc oxide gm 50 Talcgm-.. Stearic acid gm-- 5 Phenyl beta naphthylamine gmg- 5 vCarbon blackgm-- 50 Sulfur gm-- 5 For somewhat softer cured compounds applicant hasfound that beta-naphthylamine is suitable for preventing porosity, whilefor still softer stock, beta-naphthol may be used in lieu oforthotoluidine. Olen polysulde reaction products cured in accordancewith this invention have characteristics which make vthem highlydesirable as coverings for electrical conductors. The cured product isflexible and elastic, and resembles rubber in these respects. The curedproduct is rm and substantially non-porous. `The product retains itshigh resistance to oil and chemicals, and also to the effect of coronadischarge. The substance may be milled and handled in much the samemanner as rubber, and the formation of the objectionable gas during suchhandling is largely avoided. This plastic substance and the method ofcuring are disclosed and claimed in my copending application Serial No;639,733, filed October 26, 1932.

Plastics made in accordance with this invention may be used asinsulation on single or multiple strand conductors, and may be appliedin substantially the same manner as rubber, for example by extruding. Ifdesired, the olefin polysulfide plastic may replace rubber and comprisethe entire electrical insulation for'the conductor. However, it may bedesirable to cover the conductor with a sheath of rubber only slightlythinner than the normal thickness of rubber insulation, and then apply acontinuous thin protective wall of olefin polysulde plastic over therubber insulation. In such a construction the rubber is effectivelyprotected by the olen polysulfide reaction product wall against oils andacids, as well as against ozone which may be formed by corona discharge.It will be apparent that suitablejackets or armorings, for examplewrappings of cloth tape, may be applied over the insulating jacket Ainthe same manner as is done at present with rubber insulated conductors.

Referring to Figs. l and 2 there is shown merely by way of illustrationa multiple strand conductor I0 enclosed in a sheath Il of olefinpolysulde reaction product over which is a wrapping l2 of cloth tape. Amodified construction is shown in Figs. 3 and 4 in which a conductor 20is enclosed in a sheath 2l of rubber over which is a relatively thinwall 22 of olen polysulde reaction product and a spirally Wrapped clothtape 23.

The foregoing description of certain speciflc embodiments of theinvention is illustrative merely, and is not intended as defining thelimits of the invention.

I claim:-

l. An insulated electrical conductor comprising in combination aconductor, a sheath of rubber, and a relatively thinner outer sheath o fsubstantially non-porous'oleiin polysulde reaction product which hasbeen heat treated in the presence of avgas formation retarding substanceselected from the classes of aromatic amines, napthol and phenolscontaining respectively the group NH2 and the group OH combined withradicals which so limit the activity of the groups as to cause thereduction of gas formation in the product under curing conditions 2. Aninsulated electrical conductor comprising in combination a conductor, asheath of rubber, and a relatively thinner outer sheath of substantiallynon-porous olen polysulde reaction product which has been heat treatedin the presence of a primary amine substance capable of combining with agaseous product formed in the olefin polysulfide reaction product duringheating to yield a condensation product.

3. An insulated electrical conductor comprising in combination aconductor, and a sheath of a substantially non-porous plastic olefinpolysulde reaction product which has been heat treated in the presenceof orthotoluidine.

4. An insulated electrical conductor comprising in combination aconductor, and a sheath of a substantially non-porous plastic olefinpolysulde reaction product which has been heat treated in the presenceof beta-naphthylamine.

5. An insulated electrical conductor comprising in combination aconductor, and a sheath of a substantially non-porous plastic olefinpolysulfide reaction product which has been heat treated in the presenceof beta-naphthol.

6. An insulated electrical conductor comprising in combination aconductor, and a sheath of substantially non-porous olefin polysulfidereaction product which has been heat treated in the presence of aprimary amine substance capable of combining with a. gaseous productformed in the olefin polysulde reaction product during heating to yielda condensation product.

7. An insulated electrical conductor comprising in combination aconductor, and a sheath of substantially non-porous condensation productof ethylene dichloride and an alkali polysulflde which has beenheat-treated in the presence of a primary amine compound having theproperty of 'preventing or retarding the formation of gas in saidcondensation product.

8. An insulated electrical conductor comprising in combination, aconductor, a sheath of rubber, and a relatively thinner outer sheath ofsubstantially non-porous olefin polysulfide lreaction product which hasbeen heat treated in the presence of orthotoluidine.

/ 9. An insulated electrical conductor comprising in combination aconductor, and a sheath of a substantially non-porous plastic olefinpolysulide reaction product which has been heat treated in the presenceof a napthol compound which contains the group OH combined with radicalswhich so limit the activity of this group as to cause the prevention ofgas formation to take place under curing conditions.

10. An insulated electrical conductor comprising in combination aconductor, and a sheath of a substantially non-porous plastic olenpolysulfide reaction product which has been heat treated in the presenceof an amino-base compound which contains the group NH2 combined withradicals which so limit the activity of this group as to cause theprevention of gas formation to take place. under curing conditions.

11. An insulated electrical conductor comprising in combination, aconductor, a sheath of rubber, and a relatively thin outer sheath ofsubstantially non-porous olefin polysulfide reaction product Which hasbeen heat treated in the presence of beta-naphthylamine.

12. An insulated electrical conductor comprising in combination, aconductor, a sheath of rubber, and a relatively thin outer sheath ofsubstantially non-porous olen polysulde reaction product which has beenheat treated in the presence of beta-naphthol.

13. An insulated electrical conductor comprising in combination, aconductor, and a sheath of a substantially non-porous, plastic olenpolysulflde reaction product which has been heat treated in the presenceof a mono-amino derivative of an aromatic hydrocarbon of ahexacarbocyclic ring on to which is substituted an alkyl group in theortho position.

14. An insulated electrical conductor comprising in combination, aconductor, anda sheath of substantially non-porous olen polysulfidereaction product which has been heat treated in the presence of aprimary amine compound having the property of preventing or retardingthe formation of gas in said olen polysulde reaction product.

15. An insulated electrical conductor comprising in combination aconductor, and a sheath of substantially non-porous olen polysuldereaction product which has been heat treated in the presence of asubstance from the group consisting of orthotoluidine,beta-naphthylamine and betanaphthol.

16. An insulated electrical conductor comprising in combination aconductor, and a sheath of a substantially non-porous plastic olenpolysulflde reaction product which has been heat treated in the presenceof a phenol compound which contains the group OH combined with radicalswhich so limit the activity .of this group as to cause the prevention ofgas formation to take place under curing conditions.

' GEORGE SPENCER LOBDELL.

